Note: Appearance issues are often caused by caching plugins. When Posting Please Include Your URL.Search Forum Using Google Search Box AboveIMPORTANT: If after forum login, you appear logged out, click on "New Posts". You should show as logged in then. It's a Vbulletin bug.

Did you originally integrate the buttons into your old template via code? I've never heard of this problem, and I know we've got 1000's of people using sharethis.. The theme couldn't erase the code, switching to old theme should restore it. I would check the plugin settings and setup again.

I'm sorry I don't have an answer... if you're saying the code from inside a post disappeared that is very strange.. However, WP does do funky things with code when you switch from html to visual mode.. so if you did that on those posts you could have lost it.